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SOME THOUGHTS ABOUT THE THREE NEURONS IN THE VESTIBULAR OCULAR REFLEX *
Author(s) -
Baker R.,
Evinger C.,
McCrea R. A.
Publication year - 1981
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1981.tb30869.x
Subject(s) - annals , medicine , library science , history , classics , computer science
The three-neuron arc envisioned by Lorente d e N6 (1933) and popularized by Szentagothai (1943, 1950) has generated considerable scientific interest because of the apparent simplicity with which it produces compensatory eye movement following head r0tation.4'.~".~' The reciprocal organization of inhibitory and excitatory second-order vestibular neurons has offered a structural basis that adequately explains visual stabilization by coordinating the activity of agonistantagonist extraocular motoneurons. Several years ago, however, Robinson pointed to a number of problems in signal processing intrinsic to translating discharge rate on the three neurons in the vestibular ocular reflex (VOR) into muscle active-state tension.6'*'' This paper traces the development of conceptual and experimental findings, with emphasis on recent understanding of the neural signals recorded on each of the three neurons in the VOR. Although few new data are presented, a few significant insights are offered by this exercise. First, many of the recent data on neural signals in respect to information coding via discharge rate during the V O R in cat are presented, and can be compared to that in the primate. In so doing, we find that central V O R organization in the two species is very similar and suggest that neural processing may be essentially the same. Second, it is argued that understanding the three-neuron VOR pathway has important implications for studying the central organization of other oculomotor subsystems (e.g., saccadic and pursuit] hut, most relevantly, provides information concerning fixation (e.g., eye position). Third, some of the difficulties in modeling the V O R with neurons reflecting population (i.e., mean) values are discussed. The wide range of unique physiological sensitivities extending from sensory to motor periphery argues for tuned channels responding selectively throughout the oculomotor range to specific frequencies of head movement. Finally, morphological evidence pointing to the location of the integrator is suggested. This review begins by presenting the ideas underlying the type of information to be coded at the final common pathwaythe motoneuron.